with \(\mathcal {J}^{(r)}\)  defined as in Section REF . Therefore, \(V_h^{(r)}\)  is the subspace of \(V_h\)  spanned by the B-splines whose support intersect \(\Omega ^{(r)}\) . Moreover, following the notation of [1]}, we consider restriction operators \(R^{(r)}: V_h \rightarrow V_h^{(r)}\)  with \(r= 1, \ldots , N_{\mathrm {patch}}\) , defined by
\(R^{(r)} \left( \sum _{l \in \mathcal {J}} u_l B_l \right)= \sum _{l \in \mathcal {J}^{(r)}} u_l B_l\) 
